Currently it would report "operation not supported" which is confusing. Overall,
this is thinko leading to undefined behavior.

Still need to make built-ins by these names, and write tests.

If step is not constant, in first approximation, we can't apply optimization,
(well, we could, but need a special case for this).

Creating of classes (types) and instances is much more like CPython now.
You can use "type('name', (), {...})" to create classes.

Use make V=1e make V=1 or set BUILD_VERBOSE in your environment to increase build verbosity.

This should fix issue #117

Addresses issue #104.

These can be used for any object which implements stream protocol
(mp_stream_p_t).

Stream protocol is abstraction of serial I/O. Buffer protocol is
abstraction of random-access I/O. These protocols are defined down
to C level, to allow generic, while still efficient algorithms
to be coded in C (like, buffered transfer between 2 stream objects,
saving/loading of buffer object to/from stream, etc). (Note that CPython
define buffer protocol on C level, but apparently not stream protocol).